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Technology: Chemical claw could clear up radioactive spills

By
TARA PATEL in
PARIS

A chemical scoop has been successfully tested in France as a way of
trapping caesium, one of the main elements in the fallout from Chernobyl.
Even now, nearly eight years after the accident, radioactive caesium from
Chernobyl still contaminates Europe’s pastures.

Researchers from the Atomic Energy Commission (CEA) in Paris and the
University of Strasbourg believe that a family of molecules called calixarenes
could be used to manage radioactive waste. Calixarenes are complicated
organic compounds which, through a series of aromatic rings, form a chemical
‘claw’ that has the ability to trap other atoms and molecules.

In the tests, calixarene trapped up to 99 per cent of the radioactive
caesium contained in a concentrated solution of sodium nitrate. This solution
was chosen because sodium is commonly used in the treatment of radioactive
waste. The tests were part of a project, partly funded by the European Community,
to develop a way of isolating radioactive elements with extremely long half-lives
such as caesium 135.

Ten years ago American scientists discovered that a group of molecules
called crown ethers could be used to isolate caesium. Jean-Yves Barre, the
coordinator of the French project, says that calixarenes – which have been
known since 1870 – have the advantage of being practically insoluble in
water. Also they can easily release the caesium they have trapped, and
so can be reused. The CEA team says that calixarenes are much easier to
synthesise than crown ethers, and thus offer a much cheaper alternative.

But Barre warns that so far his technique has been tested only on small
volumes of radioactive solution. It may be more than a decade before the
process can be used on an industrial scale, he says.